This invention relates in general to memory systems involving encryption/decryption of data, and in particular to a memory system or method for writing data with write failure recovery capability.
Portable storage devices have been in commercial use for many years. They carry data from one computing device to another or to store back-up data. The mobile device market is developing in the direction of including content storage so as to increase the average revenue by generating more data exchanges. This means that valuable content has to be protected when stored on a mobile device. In order to protect the content stored in the portable storage devices, the data stored is typically encrypted and only authorized users are allowed to decrypt the data. This may be performed by means of an engine called a crypto-engine.
Cipher block chaining (CBC) is a method of encryption where the result (in the form of a cipher text block) of the encryption of the previous plain text block is fed back into the encryption of the next plain text block. Thus, each cipher text block is not only dependent on the plain text block, but also on previous plain text blocks. The initiation vector (IV), which is randomized data, is encrypted as the first block in the CBC process in order to provide unique input to the encryption engine, so that for a given plain text key used in the encryption, the cipher text generated would still be unique.
The CBC process is carried out by the crypto-engine which can perform encryption and/or decryption. The context of the engine refers to the current state of the engine at a given time. For a given encryption/decryption cycle, the context generated and used is unique.
When CBC is used for data encryption during a write operation, programming of the storage device may fail. In such event, the data would need to be reprogrammed to the storage device. This would require that the data that has failed to be written during the write operation be transferred again to the storage device. But once the data has already been transferred through the crypto- or encryption/decryption engine using a given context, the same data cannot pass through the engine again without re-configuring the engine with the proper context. It is therefore desirable to provide a solution for the above problem.